Method and apparatus for prechilling tap water in ice machines

Abstract: A process and apparatus (10) for prechilling tap water by using a heat exchanger (40) to provide a path of flow for the warm tap water fed into an ice maker machine (10) and another path for the cold waste water (54) ejected by the machine by means of which heat can be transferred through walls separating the fluids. The prechilling is achieved by using an insulated, elongated casing (12) having top and bottom ends (18,16) forming there between a closed reservoir (14) housing the heat exchanger (40) made of copper tubing (46) or the like. The heat exchanger is in the form of a coil (50) followed by a substantially straight tube (44) within and surrounded by the coil's turns 52). A heat-insulating hollow member (58), which is closed at one end (60), is spaced from the straight tube (44) to be surrounded by the turns (52) and to form between the hollow member (58) and the straight tube (44) an elongated chamber (64) whose bottom (59) is open to the interior of the reservoir (14).

Description: This invention relates generally to a method and apparatus for prechilling the warm drinking (tap)-water, fed into an ice maker machine to make ice cubes and the like, with the near freezing waste water ejected by the machine. Ice making machines are now widely used, especially in warm climates. They consume considerable energy some of which is unnecessarily and needlessly wasted. In the U.S.A., ice makers are certified and rated in accordance with American Refrigeration Institute (ARI) Standard 810-91. Test conditions for standard ratings are 32.22°C (90°F) ambient air, 21.11°C (70°F) tap water, and about 2.1 kg/cm 2 (30 psig) water inlet pressure. In most ice makers, and as a byproduct of the ice making process, a considerable volume of unused nearly 1°C cold waste water is now being dumped into the sewer, even though it had long been suggested to use this cold waste water for prechilling the tap water flowing into the machine, as will now be described in more detail. The lower the tap water's temperature is, the higher will be the output (harvest) of ice from the machine during each cycle of ice production. Lowering tap water's temperature by about 10°C can considerably increase the machine's ice output. A drop of 15°C in the summer would be most desirable and would produce benefits including: savings on the amount of required floor space for the ice maker, on its cost and installation, and on its operating and maintenance expenses. Workers in this ice making art had striven to arrive at practical water chilling methods and devices. U.S. patent 2,775,100, issued on Dec. 25, 1956, very briefly suggests to prechill the tap water with the cold waste water. "As the water is discharged from the tank, it proceeds to a receiver 40 where it is passed in heat exchange relation with the water being supplied" by pipe 11 (Col. 4, lns. 26-29). U.S. patent 4,338,794 shows an ice maker which prechills the tap water as well as the freon using two copper coils within two chambers of a casing. The tap water flows throuah one coil in one chamber, and the freon flows in the other coil in an adjacent chamber. Cold waste water flows through both chambers. U.S. patent 2,403,272 shows a water cooler having a refrigeration system using freon, a compressor and evaporator for cooling drinking water. The evaporator consists of a tank 1 in which a first coil 9 surrounds a second coil 8. Coil 8 is inside a pipe 11 whose bottom end opens to the interior of tank 1 and whose top end has a cold water outlet 4. The tap water fills tank 1 and pipe 11. As the freon flows under pressure throuah coils 8, 9, it changes from liquid to vapor but remains at the same cold temperature throughout this phase change and prechills the drinking water in tank 1 and in pipe 11. Should a leak occur in the freon piping, the freon will escape therefrom and contaminate the drinking water. GB patent 1 362 538 discloses within an outer casing 8 a heat exchanger connected to a primary hot water supply from a boiler. The exchanger includes a waterway 3 carrying downwardlv primary hot water through an annular gap 4 created between a coaxially arranged coiled tube 9 and a sleeve 6. The coiled tube 9 has a straight portion 11 at its upper and external end and another straight part 5 at its bottom end which is concentric with the coils convolutions. The coiled tube 9 is finned and arranged with its fins of its convolutions in contact with the outer surface of sleeve 6, around which the tube is coiled, and with outer casing 8. These points of contact create V-section waterways. The hot water is deflected by the closed end 7 of casing 8 and can only return upwardly between sleeve 6 and casing 8 through these V-section waterways. At one and the same time that the hot water is pumped over the coiled tube part, secondary cooler water from the main supply enters through straight portion 11, passes through the coiled portion of the tube, and then passes upwardly through the straight part 5. After giving up heat energy to the secondary water, the primary water leaves at point 10 from the top end of casing 8. Occlusion of the V-section waterways could be expected due to the progressive mineral and dirt sediment accumulation. Applicant was told of two tap water prechiller devices that had been introduced to the market. One proposed a copper pipe inside a plastic pipe. The tap water flowed in the copper pipe, and the cold waste water in the annular space between the two pipes. Occlusion of the annular space could be expected due to mineral sediment accumulation. The other prechiller had a reservoir in a casing containing a heat exchanger in the form of a straight copper pipe. The casing has an inlet for receiving the relatively warm tap water, another inlet for receiving the ejected cold waste water from the machine, an outlet for discharging the prechilled tap water, and an overflow tube through which the excess waste water from the reservoir can escape. The waste water warms up due to the transfer of heat from the tap water flowing in the straight pipe. As a result, the tap water's temperature flowing through the straight copper pipe decreases. It is a general object of this invention to provide an effective, efficient and compact tap water prechiller, which can be adapted for use on a wide range of ice makers from small to large sizes, and which substantially enhances the amount of heat transferred in a unit of time across a unit of surface area of the copper tubing, thereby optimally lowering the tap water's temperature per unit of casing volume. According to the present invention, prechilling the warm tap water, fed into an ice maker machine with the near freezing waste water ejected by the machine, is achieved by using an insulated outer casing forming a closed reservoir fluidly communicating with a waste water inlet, a tap water inlet, a waste water overflow outlet, and a tap water outlet. Inside the casing is a heat exchanger formed by a coiled tubing followed by a substantially straight tube portion that is surrounded by the coil's convolutions. A hollow member, closed at one end, is spaced from the straight tube so that both become surrounded by the coil's turns. The hollow member and the straight tube form an elongated chamber there between whose bottom is open to the reservoir's interior and whose top end is coupled to the waste water inlet. The coiled portion is coupled to the tap water inlet and the straight tube is coupled to the tap water outlet. In use, the tap water flows downwardly in the coil toward the lowest one of the coil's turns, and upwardly through the straight tube to the ice maker. The cold waste water flows through the elongated chamber into the reservoir and exits through the overflow outlet, thereby progressively and continuously increasing the temperature of the waste water and correspondingly decreasing the tap water's temperature. Thus the present invention is disclosed in the method claim 1 and the apparatus claim 3. Specific embodiments of the invention will be described, by way of example only, in connection with the accompanying drawings, wherein: FIG. 1 is a longitudinal sectional view of a preferred embodiment of the prechiller of the present invention; FIG. 2 is a sectional view of the prechiller taken on line 2-2 of FIG. 1; and FIG. 3 is a sectional view on line 3-3 of FIG. 2 of the long tubing from which the heat exchanger is made. In its preferred embodiment and with reference to FIGS. 1-2, the prechiller 10 of this invention has an elongated casing 12, preferably upright, which encloses a reservoir 14. Casing 12 can be a cylindrical pipe section having a bottom cap 16 and a top cap 18. It is entirely covered with a layer of thermal insulation 20. Top cap 18 has a bulkhead connector 22 for receiving tap water from line 24, and another bulkhead connector 26 through which the prechilled tap water flows out into line 28 of an ice machine 30, such as an ice cube maker used in restaurants, bars, hotels, schools, hospitals, etc. The side wall of top cap 18 has a socket 32 that receives from machine 30 ice cold waste water 54 on line 34, and a socket 36 which allows excess waste water 54 to escape to drain line 38. Within reservoir 14 is a heat exchanger 40 having a first stage 42 and a second stage 44, both stages sharing a single continuous tubing 46 of great length compared to the length of casing 12. Tubing 46 is made of a good thermal conductor preferably copper. The inlet end 48 of tubing 46 is removably coupled to connector 22, and the outlet end 49 of tubing 46 is removably coupled to connector 26. Tubing 46 in stage 42 is wound into a coil 50 having spiral turns 52 that are near to the inner wall of casing 12 (FIG.2), thereby substantially increasing the length of the path of travel for the tap water within the casing 12. In such coiling, the tube's sectional area is purposely altered from circular to substantially rectangular or oval (FIG. 3). It is believed that such an alteration favorably alters the flow and heat exchange dynamics, i.e., the heat exchange surface area relative to the volume of tap water contained within tubing 46. The portion of tubing 46 in second heat exchanger stage 44 is substantially straight and upright and will hereinafter be also designated by the numeral 44. Straight tube 44 is inside of and completely surrounded by turns 52. The bottom end of tube 44 merges smoothly with the lowest turn 52'. According to the invention, along substantially its entire length, tube 44 is surrounded by a concentric upright conduit 58, having an open end 59 and a closed off top end 60. Conduit 58 is made of a poor thermal conductor material. The space between tube 44 and the inner wall of conduit 58 forms an elongated chamber 64 for receiving waste water 54 from line 34 through socket 32 and a coupling 62. In the first ice harvest cycle, chamber 64 receives ice cold waste water 54 from line 34 which flows downwardly along and around straight tube 44, through open bottom end 59 of chamber 64, which is also the bottom of reservoir 14, and upwardly towards the top of reservoir 14, and along and around the coil's turns 52. Conduit 58 thermally isolates the colder waste water 54 in chamber 64 from the warmer waste water 54 within the rest of reservoir 14. The inlet 48 of tubing 46 receives from line 24 tap water under pressure which circulates downwardly through turns 52. The tap water flows spirally toward the lowest turn 52', thence upwardly within straight tube 44, and exits through tap water outlet 49 into feed line 28 of machine 30 for making ice. The waste water 54 in reservoir 14 cools the downwardly circulating tap water in the coil to progressively lower temperature levels while at the same time the arriving counter flowing coldest waste water 54 progressively and maximally lowers the temperature of the tap water flowing upwardly in tube 44 from which it flows out through outlet 49 into feed line 28. In chamber 64 the waste water's temperature progressively increases from top to bottom of reservoir 14. The waste water's temperature progressively increases in reservoir 14 from bottom to top, thereby resulting in a progressive rise in the temperature of the waste water surrounding tubing 46 from inlet socket 32 to to outlet socket 36, whereat it has its highest temperature, while the tap water has its lowest temperature within tube 44 at the level of socket 32. As a result, the temperature of the tap water within the entire length of tubing 46 is progressively and continuously lowered from its inlet end 48 to its outlet end 49. The changes in temperature in the waste water 54 per unit of vertical height enhances the heat transfer from the tap water flowing through tubing 46 to the surrounding waste water 54, and generates water currents within reservoir 14 which tend to maintain the surfaces of heat exchanger 40 free of sediment accumulation. It is also believed that the substantially rectangular sectional area of tubing 46 tends to improve the amount of heat transfer in a unit of time across a unit of surface area of heat exchanger 40, and in a unit of length of tubing 46. In summary, the heat exchanger's first stage 42 first prechills the fresh tap water with warmed up waste water received from second stage 44, and second stage 44 further prechills the tap water received from first stage 42 with fresh ice cold waste water received from line 34 into chamber 64. Hence, the cooling energy within the waste water discharged from ice machine 30, which would otherwise be wasted, is optimally reclaimed by heat exchanger 40 which removes heat energy from the tap water prior to injecting it into the ice making section of machine 30. Prechiller 10 is effective, efficient and compact. Using it with an ice machine will reduce the heat produced by the machine. Less "wear and tear" will be experienced by the machine's active parts. There will be less time for mineral buildup on its freeze plate, and its bin will fill up faster with ice during peak demands. It will produce more ice in the same amount -of time, or the same amount of ice in a shorter time. In the preferred embodiment for optimum thermal efficiency and adapted for use in most ice maker installations, the casing 12 had a 10.16cm (4") OD, a height of 66.04cm (26"), and a reservoir 14 of 5.451it (1.44gal). The copper tubing 46 was of refrigeration grade and had a .97cm (3/8") outside diameter (OD), a wall thickness of about .09cm (.035"), and about 7.lm (23') of copper tubing per linear 30.48cm (foot) of casing 12. In this case, the total length of tubing 46 was 14.63m (48') yielding 54 coil turns 52. Coil 50 had an outside diameter of 9.14cm (3.6") and an inside diameter of 7.37cm (2.9"). Straight tube 44 had a length of 64.77cm (25.5"). The volume of reservoir 14 with the tubing 46 inside was about 4.281 (1.13gal). For smaller ice machines, 1.22m (4') of copper tubing per linear 30.48cm (foot) of casing 12 is adequate. Other preferred dimensions include: caps 16 and 18 10.16cm (4") in diameter hollow member 46 2.54cm (1") OD, and 58.42cm (23") in length, and bulkhead connectors .97cm to .97cm (3/8" to 3/8") While it is preferred for casing 12 to remain upright, in use, the prechiller 10 will function with the casing 12 in an inclined or horizontal position but at a sacrifice in thermal heat exchange efficiency between the warm tap water and the cold waste water.

Claims: A method for prechilling the warm tap water, fed into an ice maker machine (30) to make ice cubes and the like, with the near freezing waste water (54) ejected by the machine; said prechilling using an insulated, elongated casing (12) having top and bottom ends (18,16) forming there between a closed reservoir (14) housing a heat exchanger (40) made of copper tubing (46) or the like, said casing having a waste water inlet (32), a tap water inlet (48), a waste water overflow outlet (36), and a tap water outlet (49), characterized in that the method comprises forming said heat exchanger (40) in the form of a coil (50) having a plurality of spiral turns (52) for maximum heat transfer and followed by a substantially straight tube (44) within and surrounded by said turns; spacing a hollow member (58), closed at one end (60), from said straight tube (44) so as to be surrounded by said turns (52) to form between said hollow member and said straight tube an elongated chamber (64) whose bottom (59) is open to the interior of said reservoir (14); and fluidly coupling (62) said elongated chamber to said waste water inlet (32), fluidly coupling (22) said coil to said tap water inlet, and fluidly coupling (26) said straight tube to said tap water outlet, whereby, in use, said warm tap water flows under pressure spirally toward the lowest one (52') of said turns, thence within said straight tube and through said tap water outlet into said machine for making ice, and said cold waste water (54) flows through said elongated chamber, along and around said straight tube, into the interior of said reservoir along and around said turns, and exiting through said overflow outlet, thereby progressively and continuously increasing the temperature of said waste water after it is received from said machine and progressively and continuously decreasing the temperature of said incoming tap water until it reaches said tap water outlet. The method according to claim 1, characterized in that said hollow member is heat-insulating to reduce heat transfer between said chamber (64) and said reservoir (14). An apparatus for prechilling the warm tap water, fed into an ice maker machine (30) to make ice cubes and the like, with the near freezing waste water (54) ejected by the machine after one or more ice making cycles, comprising an insulated, elongated casing (12) having top and bottom ends (18,16) forming there between a closed reservoir (14) housing a heat exchanger (40) made of copper tubing (46) or the like, said casing having a waste water inlet (32), a tap water inlet (48), a waste water overflow outlet (36), and a tap water outlet (49), characterized in that said heat exchanger (40) includes a coil (50) having a plurality of spiral turns (52) for maximum heat transfer and said-coil is followed by a substantially straight tube (44) within and surrounded by said turns; a hollow member (58), closed at one end (60), spaced from said straight tube (44) so as to be surrounded by said turns (52) to form between said hollow member and said straight tube an elongated chamber (64) whose bottom (59) is open to the interior of said reservoir (14); and means (62) fluidly coupling said chamber to said waste water inlet (32), means (22) for fluidly coupling said coil to said tap water inlet, and means (26) fluidly coupling said straight tube to said tap water outlet, whereby in use said warm tap water flows under pressure spirally toward the lowest one (52') of said turns, thence within said straight tube and through said tap water outlet into said machine for making ice, and said cold waste water (54) flows through said chamber, along and around said straight tube, into the interior of said reservoir along and around said turns, and exiting through said overflow outlet, thereby progressively and continuously increasing the temperature of said waste water and progressively and continuously decreasing the temperature of said incoming tap water until it reaches said tap water outlet, whereat it has its lowest temperature. The apparatus according to claim 3, characterized in that said hollow member is heat-insulating to reduce heat transfer between said chamber (64) and said reservoir (14). The apparatus according to claims 3 and 4, characterized in that said casing is cylindrical in shape and has an outside diameter of about 10.16cm (4") and a height of about 66.04cm (26"); said copper tubing (46) has about .97cm (3/8") OD; and the volume of said reservoir (14) without said tubing inside is about 5.45l (1.44gal) and with said tubing inside about 4.28l (1.13gal) for about 7.01m (23') of tubing per linear 30.48 cm (foot) of said casing. The apparatus according to claims 3 and 4, characterized in that said casing is cylindrical in shape and has an outside diameter of about 10.16cm (4"); and said copper tubing has about .97cm (3/8") outside diameter and a range of about 1.22m (4') of tubing per linear 30.48cm (foot) to about 7.01m (23') of tubing per linear foot. The apparatus according to claims 3 through 6, characterized in that the individual walls of said turns (52) of said coil (50) are near the inner wall of said casing (12) thereby increasing the length of the path of tap water travel within said casing. The apparatus according to claims 3 through 7, characterized in that the sectional area of said tubing (46) in said coil (50) is non circular. The apparatus according to claims 3 through 7, characterized in that the sectional area of said tubing (46) in said coil (50) is substantially rectangular in shape. The apparatus according to claims 3 through 7, characterized in that the sectional area of said tubing (46) in said coil (50) is substantially oval in shape. The apparatus according to claims 3 through 10, characterized in that said means which fluidly couple said coil to said tap water inlet is a bulkhead connector (22), and said means which fluidly couple said straight tube to said tap water outlet is another bulkhead connector (26).

Inventors: LOVE JEFF LINDEN, WELCH DANIEL LEE, LOVE, JEFF LINDEN, WELCH, DANIEL LEE
Applicants: LOVE JEFF LINDEN, WELCH DANIEL LEE, LOVE, JEFF LINDEN, WELCH, DANIEL LEE
Application year: 1994
Main classification: F25C1
IPC codes: F25C1, F28D7